1. Field of the Invention
The present invention relates to an image forming apparatus such as a printer and a facsimile machine, and particularly to an image forming apparatus having an energy-saving function to control the power supply to each of the components in the apparatus. In addition, the present invention relates to a storage medium that stores a control program for controlling this type of image forming apparatus.
2. Background Information
Recently, electrical appliance manufacturers have been proposing and developing various energy-saving products in order to address environmental protection and energy resource issues. For example, some products have a function which shifts the apparatus to a “standby” state if external input has not been actuated for a certain period of time, so as to reduce power consumption during standby and thereby save energy.
Energy saving methods mentioned above have also been very popular among image forming apparatuses such as printers and copying machines.
A conventional image forming apparatus includes various sensors used to detect the condition of the image forming apparatus so as to determine whether or not it is ready to form images, such as a toner sensor for detecting the remaining amount of developer or toner, a sensor for detecting the remaining number of recording sheets, and a jam or accumulation sensor for detecting a jam of the recording sheets. In addition, the image forming apparatus includes various sensors that are used during image forming operations, such as a registration sensor for detecting the position of one or more recording sheets during image forming operations, and a recording media discharge sensor provided adjacent to a discharge unit to which the recording sheets are discharged out of the apparatus and which detects the discharge state of the recording sheets.
In this conventional image forming apparatus, in order to effectively realize energy savings, the power supply is interrupted to different sensors in different states, such as during image formation, and in the standby state in which the sensor is not used. For example, in the standby state, the power supply is interrupted to the registration sensor and the recording media discharge sensor, which are used only during image formation.
For example, Japanese Unexamined Patent Application Publication No. 2000-278469 discloses a color electrophotographic apparatus wherein the power supply from a power source is interrupted to a toner presence detection sensor which serves to detect toner in a developer tank, or to a sheet sensor which serves to detect the remaining amount of recording sheets, while in a power-saving mode in order to save energy.
Japanese Unexamined Patent Application Publication No. H10-133465 discloses a sensor control device and sensor control method wherein the power supply is controlled so as to de-energize sensors or energize the sensors with a low current in accordance with changes to the apparatus state, such as the standby state, low power consumption mode, and an operation state, and such that the sensors can readily come back to their normal state.
However, even if the apparatus is switched from the power-saving state to image formation state, and, for example, if the temperature of a heat fixing device in the apparatus does not reach the temperature needed to fix a toner image onto a recording sheet, it is impossible to immediately start image formation.
However, in the technologies disclosed in Japanese Unexamined Patent Application Publication No. 2000-278469 and Japanese Unexamined Patent Application Publication No. H10-133465, when the power-saving state, such as a standby state and a low power consumption mode, is cancelled, power supply is quickly resumed to the sensors to which the power supply has been stopped. Consequently, power is supplied to the sensors in vain from the instant that the mode is cancelled to the instant that the apparatus is able to form an image.
Accordingly, in light of this situation, an object of the present invention is to interrupt the power supply to the sensors that are used during image formation when it is impossible to form an image, thereby providing an image forming apparatus that can save energy more effectively.